JPH0547438U - Variable displacement axial piston motor - Google Patents

Abstract

(57) [Summary] [Purpose] Compact, highly reliable and reliable speed switching is possible. [Configuration] The control ports 23 and 24 are provided at the top dead center and the bottom dead center of the valve plate 7, and hydraulic pressure is supplied to the control port 23 to set the tilt angle of the swash plate 9 to the maximum tilt angle θ ₂ , The supply line is switched to supply hydraulic pressure to the control port 24 to set the tilt angle of the swash plate to the minimum tilt angle θ ₁ . The swash plate 9 has a tilting fulcrum A on the back surface, and even when the tilting angle is switched, the center position between the fulcrums A supporting the reaction force of the piston and the position where the reaction force from the piston passes. The swash plate offset is set to zero at the intermediate tilt angle θ so that the fluctuation of the moment due to (swash plate offset) is minimized. [Effect] Compact because it does not require a swash plate angle switching cylinder. There are few moving parts and reliability is improved. The switching can be reliably performed by the self-tilting moment. Since the swash plate is not pushed from the back side, there is no risk of the swash plate 9 rising.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a variable displacement axial piston motor capable of switching between two speeds.

[0002]

[Prior Art]

 As a piston motor of this type, there is a conventional one shown in FIG. 3 (Japanese Utility Model Laid-Open No. 60-95178). In this piston motor, one end of a supported surface 55 of a swash plate 54 swingably provided with respect to a semi-cylindrical pin 53 fixed to the swash plate support surface 52 of the front casing 51 is connected to the swash plate support surface. The control piston 57 inserted into the piston chamber 56 opening at 52 pushes backward (to the left in the drawing) to change the angle of the swash plate 54, thereby switching between high speed and low speed. That is, when the hydraulic pressure is not supplied to the piston chamber 56 from the oil passage 58 provided in the front casing 51, the lower end of the swash plate 54 is moved to the front casing 51 by a spring (not shown) as shown in FIG. By being pressed, the tilt angle of the swash plate 54 becomes maximum, and high-speed operation is performed. On the other hand, when the hydraulic pressure is supplied to the piston chamber 56, the control piston 57 pushes the lower end portion of the swash plate 54 rearward, as shown in FIG. The flank 59 is pressed against the front casing 51, the tilt angle of the swash plate 54 decreases by the angle of the flank 59, and low speed operation is switched. As described above, the second speed can be switched depending on whether or not the hydraulic pressure is supplied to the piston chamber 56.

[0003]

[Problems to be solved by the device]

 By the way, the conventional piston motor has the following drawbacks. Since the piston chamber 56 is provided in the front casing 51, the size of the motor becomes large. Since the control piston 57 is required, the number of moving parts is increased and reliability is lowered. In order to supply the hydraulic pressure to the piston chamber 56, either the pilot hydraulic pipe is connected to the front casing 51 or the pilot hydraulic pipe is connected to the rear casing 60, and the above-mentioned structure is provided in the front casing 51 and the rear casing 60. It is necessary to provide a hydraulic passage that connects the pilot hydraulic pipe and the piston chamber 56. However, because of this, the size of the front casing 51 becomes large and a piping space is required around the front casing 51. However, when it is used as a wheel motor incorporated in a reduction gear (the front casing 51 is incorporated in the reduction gear), a large storage space is required in the reduction gear and the size of the reduction gear becomes large. Since the swash plate 54, which is rotatably supported by the cylindrical pin 53, is pushed by the control piston 57 from the back side, there is a risk that the swash plate 54 will float. Therefore, an object of the present invention is to provide a variable displacement axial piston motor capable of switching between two speeds, which eliminates the above-mentioned disadvantages.

[0004]

[Means for Solving the Problems]

In order to achieve the above object, the present invention has a plurality of pistons 10 fitted axially between the valve plate 7 having a high pressure port 21 and a low pressure port 22 and a swash plate 9 and axially. An internal cylinder block 6 is provided to supply the fluid from the high pressure port 21 so that the piston 10 reciprocates to rotate the rotary shaft 5, while the tilt angle of the swash plate 9 is increased. In a variable displacement axial piston motor capable of switching between high speed and low speed by changing the valve plate, the valve plate 7 is located at the top dead center and the bottom dead center between the high pressure port 21 and the low pressure port 22. 7 has control ports 23 and 24 which are symmetrical with respect to the center 25 of the cylinder 7, and have a dimension in the circumferential direction which is substantially the same as the inter-port distance of the cylinder block 6, and the swash plate 9 includes It is in contact with the casing 1 at a fulcrum A provided on the back surface of the swash plate 9, and when the fluid pressure supplied to the control ports 23 and 24 is switched, the swash plate is rotated about the fulcrum A and the swash plate is rotated. As the tilt angle of the plate 9 changes, at a tilt angle intermediate between the maximum tilt angle θ ₁ and the minimum tilt angle θ ₂ , the reaction force from the piston 10 passes through the center point between the fulcrums A. It is characterized by that.

[0005]

[Action]

In the above configuration, the tilt angle of the swash plate 9 is switched between the maximum tilt angle θ ₂ and the minimum tilt angle θ ₁ by switching the fluid pressures supplied to the control ports 23 and 24, and the high speed and the low speed 2 speed are selected. Switching is performed. In the swash plate 9, the reaction force from the piston 10 passes through the center point between the fulcrums A at a tilt angle θ intermediate between the maximum tilt angle θ ₂ and the minimum tilt angle θ ₁ . Even if the tilting angle is switched, the fluctuation of the tilting moment due to the deviation between the center point between the fulcrums A supporting the reaction force from the piston 10 and the position where the reaction force of the piston passes is minimized, and the self-tilting moment Can be reliably switched. Further, since the control ports 23 and 24 have a circumferential dimension substantially the same as the distance between the ports of the cylinder block, no confinement occurs, and the circumferential length on which the tilting moment acts becomes long. . The fluid can be supplied to the control ports 23 and 24 by providing fluid passages 33 and 34 in the casing 2 on the side opposite to the swash plate 9 and using the control pistons as in the conventional example. Since it is not necessary, the overall size of the piston motor can be reduced, and since no piping space is required around the casing 1 on the swash plate 9 side, the storage space is small when it is incorporated into a reducer, and the size of the reducer is reduced. The size can be reduced. Moreover, since the control piston is not required, the number of moving parts is reduced, and the reliability is improved. Further, unlike the conventional example, since the swash plate 9 is not pushed from the back by the control piston, there is no risk that the swash plate 9 will float.

[0006]

【Example】

 Hereinafter, the present invention will be described in detail with reference to illustrated embodiments. FIG. 1 is a sectional view of a variable displacement axial piston pump (hereinafter, simply referred to as a piston pump) according to an embodiment of the present invention, and FIG. 2 is a diagram showing a valve plate port and a hydraulic circuit of the piston pump. . In this piston pump, a cylinder block 6 is fitted to a rotary shaft 5 which is rotatably supported by a front casing 1 and a rear casing 2 via bearings 3 and 4, and a rear casing 2 behind the cylinder block 6 is fitted. The valve plate 7 is fixed to the front surface of the cradle, and the cradle type swash plate 9 is swingably supported by the support member 8 press-fitted into the front casing 1. A plurality of (9) pistons 10 are housed in the cylinder block 6 so as to be capable of reciprocating in the axial direction. A piston shoe 12 is attached to a head 11 of the piston 10, and the piston shoe 12 is fitted onto a ball retainer 15 which is biased forward (to the right in the drawing) by a spring 13 via a pin 14. It is held by the shoe retainer 16 and is in slidable contact with the swash plate 9.

As shown in FIG. 2, the valve plate 7 has two high and low pressure ports 21 and 22, and a top dead center and a bottom dead center between the two high and low pressure ports 21 and 22, respectively. It has control ports 23, 24. The two high and low pressure ports 21 and 22 and the two control ports 23 and 24 are arranged symmetrically with respect to the center point 25 of the valve plate. Further, the circumferential widths of the control ports 23 and 24 are substantially the same as the distance between the ports 26, 26, ... (shown by broken lines) of the piston holes of the cylinder block. The high and low pressure ports 21 and 22 are connected to high and low pressure lines 31 and 32 via passages (not shown) in the rear casing 2, and the control ports 23 and 24 are connected to the passage 33 in the rear casing 2. , 34 is connected to either one of the high and low pressure lines 31 and 32 via a switching valve 35 and a high pressure selecting means (shuttle valve etc.) 36, and the other is connected to the tank via the switching valve 35. It is open to 37. The high and low pressure lines 31 and 32 are connected to a reversible pump (not shown), the high pressure side and the low pressure side are switched by switching the rotation direction of the reversible pump, and the high pressure selecting means 36 selects the high pressure line accordingly.

By operating the switching valve 35, a high-pressure fluid is supplied to one of the control ports 23 and 24 from the high-pressure line selected by the high-pressure selecting means 36, and is moved to the position of the top dead center or the bottom dead center. The piston 10 is pushed by the high-pressure fluid, and the swash plate 9 is pushed by the piston 10 to have a predetermined tilt angle. That is, when the high-pressure fluid is supplied to the control port 23 provided at the top dead center, the upper part of the swash plate 9 is pressed against the support member 8 to have the maximum tilt angle θ ₂ , and the control port 23 is provided at the bottom dead center. When a high-pressure fluid is supplied to the control port 24, the lower portion of the swash plate 9 is pressed against the support member 8 to have the minimum tilt angle θ ₁ . By switching the tilt angle of the swash plate 9, it is possible to switch between high speed and low speed. The tilting fulcrum A of the swash plate 9 is located on the back surface of the swash plate 9, and the reaction force F of the piston 10 passes through the center position between the fulcrums A supporting the reaction force F from the piston 10. An angle θ (θ = (θ ₁ + θ) that is intermediate between the maximum tilt angle θ ₂ and the minimum tilt angle θ _{1 so} that the fluctuation of the moment due to the deviation from the position (hereinafter referred to as swash plate offset) is minimized. It is designed so that the swash plate offset becomes zero in ₂ ) / 2). Therefore, the switching can be surely performed by the self moment. Further, as described above, since the widths of the control ports 23 and 24 in the circumferential direction are set to be substantially the same as the distance between the ports 26 of the piston holes, the control ports 23 and 24 do not overlap the two ports 26. Therefore, no closing occurs, and the circumferential length used by the tilting moment can be increased.

As is clear from FIG. 1, this piston motor does not require a cylinder or the like for controlling the tilt angle of the swash plate 9 in the front casing 1, and the rear casing 2 has a control port. Since it is only necessary to provide the passages 33 and 34 extending to the portions 23 and 24, the casing size can be reduced and the piping space around the front casing 1 is not required. Therefore, when this piston motor is used as a wheel motor that is used by incorporating it into a speed reducer, the mounting space can be reduced and the size of the speed reducer can be reduced. Further, unlike the conventional example, since the swash plate 9 is not pushed from the back by the control piston 57, there is no danger of the swash plate 9 rising.

[0010]

[Effect of the device]

 As is apparent from the above, in the variable displacement axial piston motor of the present invention, the valve plates are symmetrical with respect to the center of the valve plate at the top dead center and the bottom dead center between the high pressure port and the low pressure port. And a control port whose circumferential dimension is approximately the same as the distance between the ports of the cylinder block, and the swash plate is in contact with the casing at a fulcrum provided on the back surface of the swash plate. , By switching the fluid pressure supplied to the control port, the tilt angle changes by rotating around the fulcrum and at the tilt angle intermediate between the maximum tilt angle and the minimum tilt angle, Since the reaction force from is passing through the center position between the fulcrums, the following effects are obtained. Even if the tilting angle is switched, the fluctuation of the tilting moment due to the deviation between the center position between the fulcrums and the position where the reaction force from the piston passes is minimized, and the switching by the self-tilting moment can be reliably performed. Since the size of the control port in the circumferential direction is approximately the same as the distance between the ports of the cylinder block, no closing occurs and the length in the circumferential direction on which the tilting moment acts becomes long. The fluid can be supplied to the control port by providing a fluid passage in the casing on the side opposite to the swash plate, and the control piston as in the conventional example is not required. In addition, because it does not require a space for piping around the casing on the swash plate side, the storage space is small when it is installed in a reducer, and the size of the reducer can be reduced. Since the control piston is not required, the number of moving parts is reduced and the reliability is improved. Unlike the conventional example, the swash plate is not pushed from the back by the control piston, so there is no risk of the swash plate rising.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a diagram showing ports of a valve plate and a hydraulic circuit in the above embodiment.

FIG. 3 is a sectional view of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Front casing, 2 ... Rear casing, 5 ... Rotating shaft, 6 ... Cylinder block, 7 ... Valve plate, 8
... Supporting member, 9 ... Swash plate, 10 ... Piston, 21, 22 ...
High and low pressure ports, 23, 24 ... Control port, 25 ... Valve plate center point, 26 ... Piston hole port.

Claims (1)

[Scope of utility model registration request] 1. A rotary shaft between a valve plate (7) having a high pressure port (21) and a low pressure port (22) and a swash plate (9).
A cylinder block (6) fitted in (5) and containing a plurality of pistons (10) in the axial direction is interposed, and the piston (10) reciprocates by the supply of fluid from the high pressure port (21). The rotary shaft (5) is adapted to rotate while the variable displacement axial piston motor is capable of switching between high speed and low speed by changing the tilt angle of the swash plate (9). The valve plate (7) is symmetrical with respect to the center (25) of the valve plate (7) at the top dead center and the bottom dead center between the high pressure port (21) and the low pressure port (22), Further, the swash plate (9) has a control port (23, 24) whose circumferential dimension is substantially the same as the inter-port distance of the cylinder block (6), and the swash plate (9) is a rear surface of the swash plate (9). Fulcrum provided in
When the fluid pressure supplied to the control ports (23, 24) is in contact with the casing (1) at (A), the swash plate (9) rotates about the fulcrum (A). As the tilt angle changes, at the tilt angle intermediate between the maximum tilt angle (θ ₁ ) and the minimum tilt angle (θ ₂ ), the piston
A variable displacement axial piston motor characterized in that a reaction force from (10) passes through a center point between the fulcrums (A).